title: Myocardial Ablation of G Protein-Coupled Receptor Kinase 2 (GRK2) Decreases Ischemia/Reperfusion Injury through an Anti-Intrinsic Apoptotic Pathway.
abstract: Studies from our lab have shown that decreasing myocardial G protein-coupled receptor kinase 2 (GRK2) activity and expression can prevent heart failure progression after myocardial infarction. Since GRK2 appears to also act as a pro-death kinase in myocytes, we investigated the effect of cardiomyocyte-specific GRK2 ablation on the acute response to cardiac ischemia/reperfusion (I/R) injury. To do this we utilized two independent lines of GRK2 knockout (KO) mice where the GRK2 gene was deleted in only cardiomyocytes either constitutively at birth or in an inducible manner that occurred in adult mice prior to I/R. These GRK2 KO mice and appropriate control mice were subjected to a sham procedure or 30 min of myocardial ischemia via coronary artery ligation followed by 24 hrs reperfusion. Echocardiography and hemodynamic measurements showed significantly improved post-I/R cardiac function in both GRK2 KO lines, which correlated with smaller infarct sizes in GRK2 KO mice compared to controls. Moreover, there was significantly less TUNEL positive myocytes, less caspase-3, and -9 but not caspase-8 activities in GRK2 KO mice compared to control mice after I/R injury. Of note, we found that lowering cardiac GRK2 expression was associated with significantly lower cytosolic cytochrome C levels in both lines of GRK2 KO mice after I/R compared to corresponding control animals. Mechanistically, the anti-apoptotic effects of lowering GRK2 expression were accompanied by increased levels of Bcl-2, Bcl-xl, and increased activation of Akt after I/R injury. These findings were reproduced in vitro in cultured cardiomyocytes and GRK2 mRNA silencing. Therefore, lowering GRK2 expression in cardiomyocytes limits I/R-induced injury and improves post-ischemia recovery by decreasing myocyte apoptosis at least partially via Akt/Bcl-2 mediated mitochondrial protection and implicates mitochondrial-dependent actions, solidifying GRK2 as a pro-death kinase in the heart.
authors.affiliation: Center for Translational Medicine, Temple University School of Medicine, Philadelphia, Pennsylvania, United States of America ; Chaoyang Hospital, Capital Medical University, Beijing, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Fan
authors.forename: Mai
authors.initials: M
authors.lastname: Chen
authors.forename: Lin
authors.initials: L
authors.lastname: Zuo
authors.forename: Xiying
authors.initials: X
authors.lastname: Shang
authors.forename: Maggie Z
authors.initials: MZ
authors.lastname: Huang
authors.forename: Michele
authors.initials: M
authors.lastname: Ciccarelli
authors.forename: Philip
authors.initials: P
authors.lastname: Raake
authors.forename: Henriette
authors.initials: H
authors.lastname: Brinks
authors.forename: Kurt J
authors.initials: KJ
authors.lastname: Chuprun
authors.forename: Gerald W
authors.initials: GW
authors.lastname: Dorn
authors.forename: Walter J
authors.initials: WJ
authors.lastname: Koch
authors.forename: Erhe
authors.initials: E
authors.lastname: Gao
mesh_terms: D000818:Animals; D017209:Apoptosis; D045304:Cytochromes c / Q000378:metabolism; D054769:G-Protein-Coupled Receptor Kinase 2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006439:Hemodynamics / Q000187:drug effects; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009203:Myocardial Infarction / Q000378:metabolism / Q000473:pathology; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000473:pathology; D009206:Myocardium / Q000201:enzymology* / Q000473:pathology; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism; D018384:Oxidative Stress; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D034622:RNA Interference; D015854:Up-Regulation; D051020:bcl-X Protein / Q000378:metabolism
chemical_list: D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; D045304:Cytochromes c; D051057:Proto-Oncogene Proteins c-akt; D054769:G-Protein-Coupled Receptor Kinase 2; D007545:Isoproterenol